The present invention relates to a slotless, brushless motor, and more especially to a driving motor which is directly connected to and used for a rotary drum of a video tape recorder (VTR).
Until now, a slotless, brushless motor has comprised a flat rotor made of a permanent magnet integrally connected with a rotary shaft, and a stator having an armature rotor in parallel to the flat rotor.
When slots are formed on the core, cogging occurs because magnetism changes at the slots during rotation. The slotless core can prevent the occurrence of cogging as well as reducing the wow flutter phenomenon of a motor.
Referring to motors employing slotless cores, U.S. Pat. No. 3,599,325 and Japanese Patent Application Laid Open No. 53-55007 are known. With these motors, permanent magnets on which eight poles are magnetized in the direction of the surface are used. Corresponding to this structure, stators manufactured by forming armature windings of three phases on flat magnetic bodies are used. According to these structures, the wiring is complicated due to the formation of armature windings of three phases on one plane and the wiring of the take-out leads is also complicated. As a result, the method for production of such an armature is complicated.
In addition, these structures fail to provide a satisfactory stability of rotation because the feed of current must be switched in turn to the armature windings of the three phases formed on the same plane.